JPH06279781A - Separation and recovery of highly unsaturated fatty acid by emulsion liquid film method - Google Patents

Abstract

PURPOSE:To provide a simple and efficient process of separating and recovering highly unsaturated fatty acids. CONSTITUTION:The separation and recovery process comprises dispersing a raw material phase comprising a substance containing highly unsaturated fatty acids in a film phase aqueous solution containing a silver salt to form an O/W emulsion and dispersing this emulsion in a recovery phase water-insoluble solvent to recover the highly unsaturated fatty acids in the recovery phase. The O/W emulsion is formed by using an emulsion stabilizer for example saponin or both saponin and ethylene glycol. By the single batch-wise operation using an emulsion liquid film highly unsaturated fatty acids and saturated fatty acids of fish oil can be quickly separated from each other.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to highly unsaturated fatty acids having a degree of unsaturation of 3 or more such as eicosapentaenoic acid and docosahexaenoic acid, and the contents of highly unsaturated fatty acids such as their esters, preferably fish oil esters. The present invention relates to a method for separating and recovering unsaturated fatty acids.

[0002]

2. Description of the Related Art Recently, highly unsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (D), which are contained in relatively large amounts in neutral lipids obtained from fish and shellfish.
The physiologically active action of HA) has received widespread attention, and establishment of advanced separation and purification methods for utilizing them as pharmaceuticals and health foods is strongly desired. However, seafood contains complex lipids such as phospholipids in addition to neutral lipids,
The amount of lipids, lipid composition, and the proportion of neutral lipids in total lipids differ depending on various factors such as the type of seafood, fishing season, fishing grounds, and oil collection methods. The neutral lipids are mainly glycerides (neutral fats). Carotenoids, hydrocarbons, sterols and their esters, free fatty acids, odorous components, etc. are contained in, and it is generally difficult to separate highly unsaturated fatty acids from seafood.

As a method for selectively separating polyunsaturated fatty acids from the contents of polyunsaturated fatty acids, a complex of highly water-soluble silver and polyunsaturated fatty acids, which is selectively water-soluble by utilizing polyunsaturation, is used. Have been developed and extracted from an aqueous layer, and then separated from the aqueous layer (JP-A-4-103558, JP-A-4-159398, and JP-A-4-218).
596, JP-A-4-243849, etc.). In these methods, it is essential to form a silver complex of highly unsaturated fatty acids, extract the aqueous complex into a water layer, and then separate fatty acids other than the highly unsaturated fatty acids that do not form a complex.

Further, it is difficult to recover highly unsaturated fatty acids from the aqueous layer containing the complex with silver, and various proposals for recovery thereof, for example, various methods for dissociating the complex. The complex dissociating agent of (4)
No. 103558, JP-A-4-218596, etc.) or heating (JP-A-4-244949)
Etc. have been proposed. In addition, JP-A-4-15489
No. 6, gazette proposes separation through a liquid membrane composed of an aqueous medium containing silver salt, but this method requires two systems of organic solvents. As described above, these methods have complicated steps and have not yet been adopted as industrial operations.

[0005]

SUMMARY OF THE INVENTION The present invention aims at simplifying and improving the efficiency of the separation and recovery process of highly unsaturated fatty acids. That is, the purpose is to efficiently separate and collect highly unsaturated fatty acids by the emulsion liquid film method. Improvement of the method known prior to the present application for selectively separating only highly unsaturated fatty acids as a silver complex from the content of highly unsaturated fatty acids, particularly forming a silver complex of highly unsaturated fatty acids in an aqueous layer It is an object of the present invention to provide a simple method that does not require an operation of separating fatty acids other than highly unsaturated fatty acids that do not form a complex after extraction.

[0006]

The present invention separates and collects highly unsaturated fatty acids by an emulsion liquid film method. A raw material phase composed of a content of highly unsaturated fatty acids is dispersed in a membrane phase aqueous solution containing a silver salt to form an O / W emulsion, and this emulsion is then dispersed in a recovery phase non-aqueous solvent to form a highly unsaturated phase. The fatty acids are recovered in the recovery phase. The O / W emulsion is formed by adding an emulsion stabilizer. As an emulsion stabilizer, saponin is used by combining it with ethylene glycol. In this method, it is not necessary to perform the operation of forming a silver complex of a highly unsaturated fatty acid and extracting it into the aqueous layer, and then separating fatty acids other than the highly unsaturated fatty acid that does not form a complex.

A method for selectively separating only highly unsaturated fatty acids from the content of highly unsaturated fatty acids as a silver complex utilizes that silver ion forms a complex with a carbon double bond of a fatty acid. In the method known before the present application, a highly unsaturated fatty acid-containing material is brought into contact with an aqueous solution containing silver ions, and a fatty acid ester having a high degree of unsaturation (eg, EPA, DHA, etc.) is distributed to the aqueous solution as a silver complex. is there. Utilizing the property that the silver ions form a complex with an unsaturated compound in the aqueous phase, the present invention attempts to promote the permeation of unsaturated fatty acids through the liquid membrane by adding silver nitrate during the liquid membrane extraction operation. It is a thing.

Higher fatty acid esters are hardly dissolved in the aqueous phase, but if the property that silver ions form a complex with an unsaturated compound in the aqueous phase is utilized, the permeation of unsaturated fatty acids through the liquid membrane can be promoted. Expected. From this, it is preferable to use as the liquid film phase, an aqueous solution of silver nitrate to which saponin as a surfactant and ethylene glycol as a thickener are added. As the content of highly unsaturated fatty acids in the raw material oil, for example, sardine fish oil ethyl ester is used. The composition of sardine fish oil ethyl ester varies depending on the place of origin and season, and the fish oil used in the examples of the present invention contains about 1.9% EPA and about 8% DHA.
Extraction should be carried out in a batch mode in a stirring tank with baffle plate, for example, after emulsifying the raw material phase and the liquid film phase at a volume ratio of 1: 1 and then adding 6 times the volume of n-hexane to the emulsion as the recovery phase. You can At this time, the target components such as EPA and DHA move from the oil phase inside the emulsion toward the oil phase outside according to the concentration gradient. This can be confirmed by sampling the recovery phase every predetermined time and analyzing it with a gas chromatograph.

In the present invention, the polyunsaturated fatty acids mean fatty acids having an unsaturation degree of 3 or more. Examples of the polyunsaturated fatty acids having the degree of unsaturation of 3 or more include α-linolenic acid, arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Therefore, polyunsaturated fatty acids include methyl ester, ethyl ester,
It includes ester type derivatives such as triglyceride, diglyceride and monoglyceride, carboxylic acid type derivatives such as amide and methylamide, and aliphatic alcohol. In the present invention, any raw material containing the polyunsaturated fatty acid having the degree of unsaturation of 3 or more can be used. Raw materials containing highly unsaturated fatty acids
Marine fish such as sardines, mackerel, saury, tuna, krill,
The raw materials can be shellfish such as shrimp itself, unrefined fish oil, animal and vegetable oils, lipids derived from microorganisms and the like at any stage of purification.

The silver salt of the present invention capable of forming a complex with an unsaturated bond is not particularly limited, and is generally soluble in an aqueous medium such as silver nitrate, silver perchlorate, silver acetate and silver tetrafluoroborate. A silver compound is used. Water is preferable as the aqueous medium of the present invention, and other compounds having a hydroxyl group such as glycerin and ethylene glycol, or a mixture thereof can be used. The molar ratio of highly unsaturated fatty acids to silver salt may be in the range of 1: 100 to 100: 1, and the concentration of the silver salt in an aqueous medium may be 0.1 mol / 1 to the saturated state. At a concentration below this, the complex is not sufficiently formed,
Polyunsaturated fatty acids are not soluble in aqueous media. From the recovery rate of highly unsaturated fatty acids, the molar ratio is 1: 5 to 1:
1, the concentration is preferably 1 to 20 mol / 1.

The D / W emulsion to which the salt of the present invention is added will be described in detail. To the content of highly unsaturated fatty acids, a silver salt aqueous solution adjusted to a predetermined concentration capable of forming a complex with an unsaturated bond is added. By shaking at a constant temperature of 25 ° C., an emulsion in which the raw material phase is dispersed in the aqueous film phase solution is prepared. At this time, an aqueous medium-soluble silver salt-polyunsaturated fatty acid complex is formed, and only the highly unsaturated fatty acid is selectively dissolved in the aqueous medium phase. Regarding the reaction temperature, the lower limit may be liquid, and the upper limit is 100 ° C.
Considering the stability of highly unsaturated fatty acids, the solubility of silver salts in water, the rate of complex formation, etc., around room temperature, reaction time 10 minutes ~
2 hours is preferred. Further, in view of the oxidation stability of highly unsaturated fatty acids and the stability of silver salt, the present invention is preferably carried out under an inert gas such as nitrogen atmosphere and protected from light.

In order to separate unsaturated fatty acid components in sardine fish oil by a liquid-liquid contacting operation such as a liquid membrane separation method, first, the distribution equilibrium with respect to an aqueous silver nitrate solution was measured, and the fish oil ester and the silver nitrate aqueous solution, and between the silver nitrate aqueous solution and hexane were measured. The equilibrium distribution of highly unsaturated fatty acid ethyl ester was investigated. An aqueous silver nitrate solution adjusted to a predetermined concentration was shaken together with fish oil ethyl ester at a constant temperature of 25 ° C. After reaching equilibrium, the fish oil phase was sampled and subjected to GC analysis. The composition of the aqueous phase was determined by mass balance.

When the ratio of fish oil to the amount of silver charged was kept constant and the change in distribution ratio when only the concentration of the silver nitrate aqueous solution was changed was plotted in the figure, the coordination number of silver ion to fatty acid was approximately calculated. The logarithmic slope represents the ethyl ester of a highly unsaturated fatty acid having 18 carbon atoms and a degree of unsaturation of 4 18 = 4 represents the ethyl ester of a highly unsaturated fatty acid having a carbon number of 16 and having an unsaturation degree of 4. The distribution ratio is about 1/4 times that of 16 = 4, which indicates that the hydrophobicity also increases as the carbon number increases. Fish oil and 5N
When the effect of the change in the volume ratio of the silver nitrate aqueous solution was examined, the distribution ratio of fatty acids generally decreased as the volume of fish oil increased. This is probably because there is an upper limit to the solubility of unsaturated fatty acids in the aqueous silver nitrate solution.
Only 16 = 4, which represents an ethyl ester of a polyunsaturated fatty acid having a carbon number of 16 and a degree of unsaturation of 4, has a larger distribution ratio as the volume ratio of fish oil increases. It is presumed that it has a high affinity for the silver nitrate aqueous solution. Next, an experiment was conducted on the partition between the recovery phase and the membrane phase. The fish nitrate and silver nitrate were brought into contact with each other at a volume ratio of 1: 2 to reach the distribution equilibrium, and then the silver nitrate aqueous solution was separated from the fish oil by using a separating funnel and brought into contact with n-hexane to obtain a silver nitrate aqueous solution.
The distribution coefficient of fatty acids between hexanes was measured. From the relationship between the concentration of the hexane phase in the equilibrium state and the concentration of silver nitrate in the aqueous phase, and the relationship between the distribution ratio and the concentration of silver nitrate, when the concentration of silver nitrate is low, most of the unsaturated fatty acids move to the hexane phase, but the aqueous solution Since the component contained in is originally small, the solute concentration in the hexane phase is low. If the silver nitrate concentration is high,
Since the amount dissolved in the aqueous solution was large and the distribution ratio was also large, the concentration of unsaturated fatty acids in the hexane phase decreased.

Effect of Silver Nitrate Concentration The silver nitrate concentration is a major factor in determining the solubility of unsaturated fatty acids in the liquid film phase. Liquid membrane phase charged to a concentration of 1M silver nitrate
Experiment was performed by changing from 1 to 3M. As a result, in the experiment with a silver nitrate concentration of 1M, it was found that the progress rate of the extraction reaction was considerably slower than that of 3M. It is considered that this is because the solubility of unsaturated fatty acids in the film phase depends largely on the silver concentration. When the concentration of silver nitrate is high, the rate of permeation of unsaturated fatty acids increases, but the stability of the emulsion decreases because the density difference between the liquid film phase and the fish oil phase increases.

Effect of Surfactant When the effect on the stability of the liquid film was examined by changing the amount of saponin added, it was revealed that the stability of the liquid film can be remarkably improved by adding saponin. . It was found that when ethylene glycol was added as a thickener, the film destruction was further suppressed.

Effect of Stirring Speed The effect of stirring speed on the stability of the liquid film and the permeation rate of EPA was examined. When the stirring speed was slow, the emulsion stagnated at the bottom of the stirring tank, but the stirring speed When it becomes faster, it becomes droplets and disperses in the recovery phase. When the stirring speed is sufficiently high, the contact area between the liquid membrane phase and the recovery phase becomes very large, and the amount of permeated components transferred to the recovery phase per unit time increases dramatically. On the other hand, it was found that the dropletized emulsion was repeatedly dispersed and coalesced in the stirring tank, and the renewal of the emulsion-recovery phase interface caused a remarkable film breakage and lowered the stability of the liquid film.

[0017]

EXAMPLES The present invention will be described with reference to examples. Examples Higher fatty acid esters are hardly dissolved in the aqueous phase, but if the property that silver ions form a complex with an unsaturated compound in the aqueous phase is utilized, the permeation of unsaturated fatty acids through the liquid membrane can be promoted. It is expected to be. For this reason, a solution obtained by adding saponin as a surfactant and ethylene glycol as a thickener to an aqueous solution of silver nitrate was used as a liquid film phase. Sardine fish oil ethyl ester was used as the raw material phase. The composition of sardine fish oil ethyl ester varies depending on the production area and season. The fish oil used is approximately 19% EPA and DH.
It contains about 8% of A.

In the extraction experiment, the volume ratio of the raw material phase and the liquid film phase was 1:
After emulsifying in step 1, n-hexane of 6 times the volume of the emulsion was added as a recovery phase, and batch operation was performed in a stirring tank equipped with a baffle plate. At this time, the target components such as EPA and DHA move from the oil phase inside the emulsion toward the oil phase outside according to the concentration gradient. The recovery phase was sampled every predetermined time and analyzed by gas chromatography.

FIG. 1 shows an extraction experiment of a typical emulsion liquid membrane operation. The component names are represented by the number of carbon atoms and the number of unsaturated bonds except EPA and DHA. The liquid film phase was a 3M silver nitrate aqueous solution containing 0.5 wt% saponin and 30 wt% ethylene glycol, and an experiment was conducted at an operating temperature of 15 ° C. and a stirring speed of 600 rpm. Since the recovery rate of unsaturated fatty acids increased sharply after 1 minute of operation time, reached the maximum value after 10 minutes, and gradually decreased thereafter, it is considered that the extraction phenomenon is almost completed in the first minute. To be On the other hand, the saturated fatty acid is hardly dissolved in the aqueous phase, and therefore the recovery rate thereof indicates the rate of migration into the recovery phase due to the destruction of the liquid film.

There are two possible routes for the movement of the components in fish oil from the oil phase inside the emulsion to the oil phase outside. One is diffusion transfer through the liquid film phase, and the other is a phenomenon of mixing of the inner oil phase with the outer oil phase due to liquid breakage. Saturated fatty acids appear to be dominated by membrane disruption migration, whereas unsaturated fatty acids need to consider the contributions of both diffusional migration and membrane disruption migration. Assuming that the amount of unsaturated components dissolved in the membrane phase is sufficiently small, determine the composition in the oil droplets in the emulsion from the mass balance, and recover the unsaturated fatty acids using the membrane destruction rate obtained from the saturated fatty acid recovery rate. The contribution of diffusive migration to the rate was calculated. The calculated values are shown in Table 1 (maximum concentration rate and separation coefficient in emulsion liquid membrane extraction). From this result, EPA and DHA with operating time from 1 to 10 minutes
It is considered that the increase in the recovery rate is mostly due to the film destruction.

[0021]

[Table 1]

The liquid film phase was an aqueous silver nitrate solution containing 0.5 wt% saponin and 30 wt% ethylene glycol, and the influence of the silver nitrate concentration was investigated by changing the concentration of the aqueous silver nitrate solution at an operating temperature of 15 ° C. and a stirring speed of 600 rpm. The results are shown in FIG. 2 (silver nitrate concentration and liquid film stability) and FIG. 3 (silver nitrate concentration and EPA recovery rate).

The liquid film phase is saponin and ethylene glycol 3
A 3M silver nitrate aqueous solution containing 0 wt% was added, and the operating temperature was 15
The effect of the surfactant was investigated by changing the amount of saponin added at 0 ° C. and a stirring speed of 600 rpm. The results are shown in FIG. 4 (effect of saponin addition amount on liquid film stability).

The liquid film phase was a 3M silver nitrate aqueous solution containing 0.5 wt% saponin and 30 wt% ethylene glycol,
At an operating temperature of 15 ° C., the effect of stirring speed was examined by changing the stirring speed. The results are shown in FIG. 5 (influence of stirring speed on membrane destruction rate) and FIG. 6 (influence of stirring speed on EPA recovery rate).

[0025]

INDUSTRIAL APPLICABILITY The present invention is a method capable of rapidly separating highly unsaturated fatty acids and saturated fatty acids in a highly unsaturated fatty acid-containing material such as fish oil by a one-step batch operation using an emulsion liquid membrane. Can be provided.

[Brief description of drawings]

FIG. 1 is a view showing a change with time of a fatty acid recovery rate by an emulsion liquid film.

FIG. 2 is a diagram showing the silver nitrate concentration and the stability of a liquid film.

FIG. 3 is a diagram showing a silver nitrate concentration and an EPA recovery rate.

FIG. 4 is a diagram showing the influence of the amount of saponin added on the stability of a liquid film.

FIG. 5 is a diagram showing the effect of stirring speed on the film destruction rate.

FIG. 6 is a diagram showing the influence of the stirring speed on the EPA recovery rate.

Claims (4)

[Claims] 1. An O / W emulsion is formed by dispersing a raw material phase composed of a content of highly unsaturated fatty acids in an aqueous membrane phase solution containing a silver salt, and then the emulsion is dispersed in a recovery phase non-aqueous solvent. A method for separating and recovering highly unsaturated fatty acids, which comprises recovering highly unsaturated fatty acids in a recovery phase. 2. The method for separating and recovering highly unsaturated fatty acids according to claim 1, wherein an O / W emulsion is formed by adding an emulsion stabilizer. 3. The method for separating and recovering highly unsaturated fatty acids according to claim 2, wherein the emulsion stabilizer is saponin. 4. The method for separating and recovering highly unsaturated fatty acids according to claim 2, wherein the emulsion stabilizer is saponin and ethylene glycol.